In the X-ray medical examination, lead line grids are placed over the X-ray films to screen secondary radiation from the film and improve the quality of radiographs. However, the grid lines show on the film unless the grid is moved in the direction perpendicular to the lines at a speed that several grid lines pass a given point on a film during an exposure. For this reason the speed of the grid travel is very critical for obtaining line-free radiographs.
For extremely short exposures, the grid has to be accelerated very rapidly to prevent the grid lines from being photographed. And additionally, the grid has to move far enough to erase minor irregularity in the grid pattern. Traditionally, an actuator for a grid comprises a small electric motor with a gear drive to move the grid over the film and is disposed on the side in the Bucky.